Abstract
The observation of active Ti-44 in supernova remnants offers the potential to solve one of the most debated questions in modern astrophysics, the exact underlying explosion mechanism of core collapse supernovae (CCSNe). In particular, a comparison between the predicted synthesized yield of Ti-44 and the ejected flux is expected to allow for a determination of the mass cut of the star. Unfortunately, such comparisons are currently severely hindered by large uncertainties in the nuclear reactions governing the production and destruction of Ti-44. On this note, the astrophysical V-45(p, gamma)Cr-46 reaction is expected to play a decisive role. We present the first experimental information on resonant states in the V-45(p, gamma)Cr-46 reaction. Excitation energies have been measured with high precision for ten previously unknown, low-spin, proton-unbound states in Cr-46, and spin-parity-assignment constraints have been made using observed gamma-decay patterns and shell-model calculations. We find that an l = 1 resonance at 714 keV dominates the V-45(p, gamma)Cr-46 reaction for the entire temperature range of alpha-rich freezeout. Moreover, the nominal rate is found to be similar to 25-50% of previous estimates for T > 1.2 GK, indicating an increase in Ti-44 production in CCSNe of similar to 20-35%.